Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $207.61   13.480%   $235.5958   $235.60   $235.60   $235.60  
  Purchase #2 $243.78   7.205%   $261.3443   $261.34   $261.35   $261.30  
  Purchase #3 $44.39   5.458%   $46.8128   $46.81   $46.80   $46.80  
  Purchase #4 $78.29   10.499%   $86.5097   $86.51   $86.50   $86.50  
  Purchase #5 $24.90   6.294%   $26.4672   $26.47   $26.45   $26.50  
  Purchase #6 $196.83   11.578%   $219.619   $219.62   $219.60   $219.60  
  Purchase #7 $220.25   5.198%   $231.6986   $231.70   $231.70   $231.70  
  7 purchase totals = $1,016.05       $1,108.0474   $1,108.05   $1,108.00   $1,108.00